Quote Originally Posted by panopticon View Post
Canon's 17-55mm IS f/2.8 and Tokina's 11-16mm lenses [...] I find myself using my zoom lenses in their fully extended or retracted positions the most (~90% of the time). I interpret this as a possible indicator that perhaps I should try my luck with primes instead on my next setup.
Well, your three focal lengths are approximately 11mm, 17mm, and 55mm. In full frame that's approximately 18mm, 28mm, and 90mm. Having one prime at each of those focal lengths seems like an excellent setup to me!

How about this?
Zeiss 18mm f/3.5 (manual focus, slow, 1 pound).
EF 28mm f/2.8 IS (not out yet, but only half a pound).
EF 100mm f/2.8 IS (1 and a half pounds).

Here's another possibility that's based on wider angles of view than what you had with the 50D:
Rokinon 14mm f/2.8 (manual focus, but cheap and 1 pound)
24mm f/1.4 II (1 and a half pounds)
85mm f/1.8 (1 pound)

The very lightest kit I can think of (2 pounds for all three):
EF 20mm f/2.8
EF 50mm f/1.8
Tamron 90mm f/2.8